454 Clarke and Schneider — Experiments upon the 



position of both minerals reduces to very simple terms ; one 

 term being a normal hydro-mica. In the jefferisite we have 

 approximately A10 a MgSi0 4 R , s .3H a O + Al 2 (Si0 4 ) 3 Mg 2 H 2 . 3H 2 ; 

 or a mixture in equal ratios of a hydro clintonite and a hydro- 

 biotite, the alkalies being replaced by hydrogen, and E/ being 

 in part, about one-third, MgOH. The greatest uncertainty is 

 in the loosely combined water, which is probably analogous to 

 the water in laumontite. Two-thirds of the 3H 2 is of this 

 type ; the remaining one molecule being given off below 300°. 

 Dried at 100° the salts become monohydrated. Reducing the 

 bases of the analysis to terms of alumina and magnesia we get 

 the following comparison with the formula : 



Found. 



Si0 2 34-97 



A1 2 3 21-91 



MgO ._ -. 21-51 



H 2 constitutional .. 6*52 



H 2 0, 250°-300° 4-30 



HO, over H SO 10-79 



Calculated 



34 



00 



21 



67 



22 



67 



6 



37 



5 



10 



10 



19 



100-00 100-00 



The concordance here is less perfect' than in the previous 

 cases, but for obvious reasons. First, the uncertainty in the 

 water has already been mentioned. Secondly, the actual ratio 

 between the clintonite and biotite molecules, as deduced from 

 the empirical formula, is not 1 : 1 but 13 : 15. Finally the ob- 

 served MgOH is a little less than one-third R/ 3 . Still, consid- 

 ering the character of the mineral, the agreement between 

 analysis and theory is as close as could be expected. 



For kerrite, uniting the univalent factors, the formula be- 

 comes 



R% 4 R'' 61 R' 72 (Si0 4 ) 63 7 .75H 2 



This, very nearly, is equivalent to 



A10 2 MgSi0 4 R' 3 .3H 2 + A](Si0 4 ) 3 Mg 3 H 3 .3H 2 0, 



commingled in the ratio of 1:5, with two-thirds of R/ s being 

 MgOH. The second term in this mixture is a hydrous j)hlogo- 



Calculated. 

 Found. As given. As a pblogopite. 



SiO„ 38-51 38-33 41-66 



Al 2 6 3 12-79 12-38 11-84 



MgO 28-02 29-12 27-77 



H^O, constitutional-.. 6-61 6'55 6-25 



H 2 0, at 250°-300° 4-35 4-37 4"16 



H 2 0, over H 2 S0 4 9-72 8-75 8-32 



100-00 100-00 100-00 



